Hydraulic contol unit

ABSTRACT

A grommet for a bore in a hydraulic modulator comprises a plurality of ribs disposed about a periphery of the grommet, and a lip seal extending between the ribs. The ribs are adapted to engage the bore, and the lip seal is adapted to engage the bore at an interface to prevent passage of fluid in one direction past the interface.

TECHNICAL FIELD

[0001] This invention relates generally to braking systems for motor vehicles, and relates more particularly to a hydraulic control unit for an anti-lock braking system of a motor vehicle.

BACKGROUND OF THE INVENTION

[0002] Antilock brake systems (“ABS”) are hydraulic braking systems for motor vehicles. A typical ABS system senses when the wheels on a vehicle begin to lock up during braking, and modulates at a relatively high rate hydraulic pressure at the affected wheel brake(s). The high rate of braking cycles creates a certain degree of vibration and corresponding noise in the ABS assembly, which can intrude into the passenger compartment of the vehicle. Such vibration and noise may be objectionable to the passengers in the vehicle.

[0003] A vehicle braking system typically includes a number of devices that cooperate to control fluid pressure in the vehicular braking system, and in particular within the anti-lock braking system. One such device is a hydraulic control unit. An ABS hydraulic unit normally includes positive displacement pumps that may weep a small amount of brake fluid during operation. This residual fluid must be routed away from any nearby electrical components, and is typically vented outside the ABS hydraulic assembly.

SUMMARY OF THE INVENTION

[0004] This invention is a grommet for a bore in a hydraulic modulator. The grommet comprises a plurality of ribs disposed about a periphery of the grommet, and a lip seal extending between the ribs. The ribs are adapted to engage the bore, and the lip seal is adapted to engage the bore at an interface to prevent passage of fluid in one direction past the interface.

[0005] Accordingly, it is an object of the present invention to provide a grommet of the type described above that allows fluid weeping from the reciprocating piston pump assemblies within the brake control unit to be released outside the unit, while maintaining an external environmental seal.

[0006] Another object of the present invention is to provide a hydraulic control unit that includes an isolated mounting interface to the vehicle.

[0007] Still another object of the present invention is to provide an isolation boot for the terminals of a motor for the hydraulic modulator.

[0008] The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a side view of an electro-hydraulic control unit for the braking system of a motor vehicle;

[0010]FIG. 2 is a perspective view of one embodiment of a grommet for use with the electro-hydraulic control unit;

[0011]FIG. 3 is a cross-sectional view of the grommet;

[0012]FIG. 4 is a perspective view of a motor terminal boot for use with the electrohydraulic control unit;

[0013]FIG. 5 is a cross-sectional view of the motor terminal boot; and

[0014]FIG. 6 is a cross-sectional view a portion of the electro-hydraulic control unit and another embodiment of the motor terminal boot.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0015]FIG. 1 shows an electro-hydraulic control unit (EHCU) 10 including an electrical control unit (ECU) 12 and a hydraulic modulator 14. As is well known, the ECU 12 normally contains the electronic components, and the hydraulic modulator 14 normally contains the hydraulic components, for modulating fluid pressure in the braking system of a motor vehicle. The hydraulic modulator 14 includes a motor 16 that powers a reciprocating piston pump (not shown). The pump in turn develops fluid pressure to return fluid to a vehicle master cylinder, or to generate a braking force at the wheels of the motor vehicle.

[0016] The motor 16 extends into a cavity in the hydraulic modulator 14. An egress path for hydraulic fluid that may accumulate in the cavity is provided through a vertically oriented, generally orthogonal drainage hole 20 that originates at a pump bore/motor cavity in the hydraulic modulator. The drainage hole 20 passes through a motor terminal bore 42 that facilitates the connection of the terminals of the motor 16 to the ECU 12, and opens into a larger diameter bore 22 machined into the body of the hydraulic modulator 14. A grommet 24 is disposed into the bore 22.

[0017]FIGS. 2 and 3 show the grommet 24 in greater detail. The grommet 24 includes a plurality of extruded ribs 26 disposed about its periphery, and a lip seal 32 extending between each pair of ribs. The grommet 24 also includes a central bore 34 which is adapted to accept a solid peg or other mounting member for mounting the modulator 14 to the vehicle. Because the modulator 14 develops some vibrations in operation, the grommet 24 is preferably formed of an elastomer such as rubber to facilitate the isolation of these vibrations.

[0018] The grommet 24 is inserted tapered end first into the bore 22. The ribs 26, preferably three of which are equally spaced around the outside of the grommet, ensure consistent location of the grommet 24 with the inside diameter of the bore 22. The insertion of the ribs 26 within the bore 22 also radially compresses the grommet 24, and in particular a plurality of open areas 36 and 38 extending from opposite faces of the grommet, to facilitate tuning of the vibrational damping. When in place, the tapered shape of the lip seal 32 around the periphery of the grommet 24 essentially functions as a check valve to prevent entry of external environmental debris, while allowing any excess brake fluid from the pump assemblies traversing down through the drain hole 20 to pass the lip seal and exit out of the bottom of the modulator 14.

[0019] Referring again to FIG. 1, the EHCU 10 also includes a boot 40 for the terminals electrically connecting the ECU 12 with the motor 16. The motor terminal boot 40 is closely disposed in the orthogonally drilled bore 42 in the modulator body, and extends between the underside of the motor 16 and a location proximate the underside of the ECU 12. Residual brake fluid may also accumulate in the motor terminal bore 42. To accommodate this, the motor terminal boot 40 is configured to prevent brake fluid from traveling into the motor 16, as well as to prevent fluid from traveling into the ECU 12.

[0020]FIGS. 4 and 5 show the motor terminal boot 40 in greater detail. The motor terminal boot 40 is generally cylindrical, and includes a tapered end 44 and an opposite, motor-side end 46. The tapered end 44 has a lip seal 48 to prevent any fluid in the terminal bore 42 from entering the ECU 12, while at the same time allowing the ECU to vent back through the lip during any high temperature excursions. The end 46 of the motor terminal boot includes an enlarged diameter region 50 that may either be wedged into the terminal bore 42, or disposed against a shoulder 52 in the modulator body as shown in FIG. 1. In the latter case, the enlarged region 50 may be flattened to more effectively abut against the shoulder 52. In either case, any residual brake fluid that accumulates in the motor terminal bore 42 and outside the boot 40 may travel down the vertical drill 20 and out through the grommet 24, as discussed above.

[0021]FIG. 6 shows an alternative embodiment 60 of the motor terminal boot. The motor terminal boot 60 is stepped to include separate face seals 62 and 64. To accommodate the shape of the motor terminal boot 60, the terminal bore 42′ is correspondingly stepped to include sections 66, 68 and 70. Upon installation, the larger outside diameter face seal 62 is compressed between the motor 16 and a shoulder 72 extending between the sections 66 and 68. This compressive force ensures that the smaller outside diameter face seal 64 remains viable at a shoulder 74 extending between the sections 68 and 70 for protection of the ECU 12. As with the motor terminal boot 40, any residual brake fluid that accumulates in the motor terminal bore 42′ and outside the double-faced motor terminal boot 60 may travel down the vertical drill 20 and out through the grommet 24.

[0022] While the embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein. 

1. A grommet for a bore in a hydraulic modulator, the grommet comprising: a plurality of ribs disposed about a periphery of the grommet, the ribs being adapted to engage the bore; and a lip seal extending between the ribs, the lip seal being adapted to engage the bore at an interface to prevent passage of fluid in one direction past the interface.
 2. The grommet of claim 1 wherein the grommet includes a central bore.
 3. The grommet of claim 1 wherein the grommet is formed of an elastomer.
 4. The grommet of claim 1 wherein the grommet is formed of rubber.
 5. The grommet of claim 1 wherein the grommet includes at least one open area adapted for compression when the ribs engage the bore in the hydraulic modulator.
 6. A grommet for a hydraulic modulator, the grommet comprising; a plurality of ribs disposed about a periphery of the grommet, the ribs being adapted to engage a bore in the hydraulic modulator; and a lip seal extending between the ribs, the lip seal being adapted to engage the bore to permit passage of fluid away from the hydraulic modulator.
 7. The grommet of claim 6 wherein the grommet includes a central bore.
 8. The grommet of claim 6 wherein the grommet is formed of an elastomer.
 9. The grommet of claim 6 wherein the grommet is formed of rubber.
 10. The grommet of claim 6 wherein the grommet includes at least one open area adapted for compression when the ribs engage the bore in the hydraulic modulator.
 11. A hydraulic control unit comprising: an electrical control unit; a hydraulic modulator having a bore and a drain hole for draining fluid into the bore; and a grommet having a periphery and a plurality of ribs disposed about the periphery and engaging the bore in the hydraulic modulator, and a lip seal extending between the ribs and engaging the bore to permit passage of fluid away from the hydraulic modulator.
 12. The hydraulic control unit of claim 11 wherein the grommet includes a central bore.
 13. The hydraulic control unit of claim 11 wherein the grommet is formed of an elastomer.
 14. The hydraulic control unit of claim 11 wherein the grommet is formed of rubber.
 15. The hydraulic control unit of claim 11 wherein the grommet includes at least one open area adapted for compression when the ribs engage the bore in the hydraulic control unit.
 16. The hydraulic control unit of claim 11 further comprising a motor having at least one terminal and a boot disposed around the at least one terminal.
 17. The hydraulic control unit of claim 16 wherein the boot is disposed in a terminal bore and includes a lip seal.
 18. The hydraulic control unit of claim 17 wherein the boot includes an enlarged diameter region engaged with the terminal bore.
 19. The hydraulic control unit of claim 16 wherein the boot is stepped to include at least two face seals. 